The invention relates to a DC-DC converter and, in particular, to a DC-DC converter for a display panel.
Due to high carrier mobility, low temperature poly-silicon (LTPS) technology makes it possible to integrate peripheral circuits on a glass substrate. With this technology, some integrated circuit (IC) functions can be implemented with circuits of thin film transistors fabricated on the glass substrate.
Integration of DC-DC converters on glass substrate simplifies implementation and reduces costs of integrated circuits. However, clock skew often occurs during clock pulses because of loading effect on the panel. This phenomenon causes charge-sharing problems, leading to performance degradation.
FIG. 1 is a schematic diagram of a conventional DC-DC converter in a display panel. In this architecture, the DC-DC converter 102 is far from a clock signal generator and thus the loading effect of the panel distorts the clock signal.
FIG. 2 is a circuit diagram of a conventional DC-DC converter. In this structure, the clock signal is distorted by the loading effect. Switch transistors 202, 202′ cannot be fully turned on or off in time, resulting in charge-sharing problems. The output voltage of the DC-DC converter is also affected.
FIG. 3 is a circuit diagram of another conventional DC-DC converter. The DC-DC converter is divided into a switch control and a charge pumping part. A coupling pair 306 generates control signals for control of the switch transistor 302. However, the skewed clock signal is transmitted to the switch transistor 302 through the coupling capacitors 304, 304′. Since clock skew of the input clock signal still exists, the charge-sharing problem affects the efficiency of the charge pump in the DC-DC converter.